Solar collector

ABSTRACT

Disclosed is a solar heater with a primary circuit course in a panel for heating two separate inter connected storage reservoirs.

1. HISTORICAL FRAMING

Since some year ago, I began to become interested by the use of solar energy to heat domestic water.

So I started to sell same Portuguese solar heater systems that were available in the Portuguese market.

The low performance of those systems, make ours clients to began disappointed, because electric energy (supplementary energy for this systems) consume was high.

So tried to find outland solutions that could be more efficient.

All that work was inutile because those systems had almost the same performance.

Since then, I really would like to do something to develop those kinds of systems, to my clients became satisfied.

After thinking of the problem, arise some ideas.

The results were amazing.

The high performance is the result of association between panels, as well as a utilization of a high stratification reservoir (which the cold water that enter does not mix with the warm water that goes to consume, and just after the first 150 litres are sufficiently warm is when it start to heat the others 150 litres).

So, we obtain a much better performance that implies water much more warm for the same solar radiation.

From now on, I'm gone explain how does the others solar heater systems works, and then I will confront with my system.

2. THE WAY THAT THE OTHERS SOLAR HEATER SYSTEMS WORK

The solar heaters Kits to get domestic water warm are composed by a primary circuit, which has fifteen litres on an average.

This circuit works just with the gravity force and by density water alteration, because of temperature variation.

So, in case of solar radiation, the water in the primary circuit is constantly doing the course from the panels to reservoir (where happens the heat transference to the consume water) and then from the reservoir to the panels.

In the others Kits (See FIG. 1), the water course in the primary circuit is:

a) The water less warm that had just gone out of reservoir goes down by an exterior tube, out of the heater zone (FIG. 4, number 1) and by that fact causes same performance wastes.

b) When the water comes into the panels, and supposing that each panel has two metros height and one width, will go four metros long inside the heater zone (See FIG. 4).

So, whichever is the watercourse inside the tubes, it will go through two metros outside the heater zone and four metros inside the two panels.

c) The water when returns to reservoir, transfer all the heat for just one reservoir witch means that in case of low solar radiation days, the temperature water raise in all reservoir is not enough to any kind of warm water use.

d) By the fact of the others solar heater Kits has just one reservoir, the consume cold water that enter will directly mix with the warm water that goes out, that is a very unfavourable mix.

3. THE WAY THAT OUR SOLAR HEATER SYSTEM WORK

In our system the primary circuit course is completely different (See FIG. 3 to understand)

a) The main question is to know how possible is the water go down, after gone out of the reservoir, if it is in the heater zone and so wants to go up.

That is possible because of the stopper (See FIG. 2, A-A′ cut)

So, in each panel of 10 tubes, in nine tubes the water power that is imposed when wants to go up is enough to happens a sucking in the other tube, where the water even warming up is going down.

b) Because there are no connections between panels in the inferior side (See FIG. 2), the water is forced to enter in the second panel in the superior side.

c) So the course of this primary circuit is 10 metros long inside the heater zone, really bigger than the four metros of the others systems (See FIG. 3).

And by that fact the water in our primary circuit is much more warm.

d) The reservoir has two permuting in distinct reservoirs (See FIG. 2).

So the water that comes from the panels and enter in first permuting will start warming up the consume water in the left reservoir, and so when the water enters into the second permuting (that is in the right reservoir), it's already with a temperature much inferior (minim consume water temperature of the left reservoir).

So, for example, if the water arrives at the first permuting with 80° degrees temperature, may cause a consume water temperature of 50° degrees in the superior side of the reservoir and 30 degrees in the inferior side (for that happens the heat transfer was already too much), and then the primary circuit water that arrives to the other permuting is no much more then 30 degrees and so will not warm up significantly the consume water of the right reservoir.

As long as the consume water temperature of the left reservoir grows, more will be the heat transfer for the second reservoir.

So, if we already have 70° degrees temperature in the superior side of the first reservoir and 50° degrees temperature in the inferior side, the primary circuit water that arrives to the second permuting is already with 50° degrees and continues warming up the consume water of the second reservoir.

e) The cold consume water that enters in the right reservoir (the reservoir that has less warm water) will not directly mix with the hot water that goes to consume (goes out from the left reservoir) (See FIG. 2) and by that fact doesn't provoke big temperatures breaks between the water that goes to consume and the cold consume water that enters.

f) The consume water that goes from the right reservoir to the left reservoir is still forced to go to the bottom of left reservoir with the same objective, that is retard how far is possible the “contact” between the consume water that enters and the one that goes out.

So, for example, if the consume water enters with 15° degrees temperature, it might grow up for 35° in the first reservoir and then in the second reservoir can grows from 35° to 50° degrees that implies there are not a thermal “shock” between the consume water that enter and the one that goes out. 

1. Solar system for heating domestic water that comprises solar panels functioning in series, which have a primary circuit containing a fluid that passes between heat exchangers (9 and 10) mounted on tanks (3 and 4) containing piped water to be heated and the tubes (15, 25, 20 and 24) and (16, 26, 21 and 27) of the panels (6 and .5), characterized in that the said fluid of the primary circuit circulates by thermosyphon effect, the fluid of the primary circuit that comes from the exchanger (10) entering directly into panel (6) through tube (15) and being heated immediately even though it is flowing downwards.
 2. Solar system for heating domestic water according to claim 1, characterized in that the thermosyphon effect in the panels (6 and 5) is achieved by the total closure (1-1′) of the upper tube (24), which forces the fluid to travel (18) down tube (15), while it is being heated, circulating to tube (25) and flowing up tubes (20) to tube (24), from which it passes to the adjacent panel (5), and due to the partial closure (2-2′) of tube (27), the fluid is forced to travel (18) down tube (16), circulating to tube (26) and flowing up tubes (21) to tube (27), the end of which is connected to the exchanger (9) of tank (3).
 3. Solar system for heating domestic water according to claim 1, characterized in that the downwards path of the fluid of the primary circuit in vertical tubes (15 and 16) is ensured by the suction caused by the fluid flowing up tubes (20 and 21), due to the fact that the latter tubes are greater in number than the single tube (15 and 16) in each of the panels.
 4. Solar system for heating domestic water according to claim 1, characterized in that the partial closure (2-2′) permits the passage of air in order to allow the fluid to circulate and the panels to be filled, i.e. if we fill the primary circuit through tube (7), the water will reach tube (25) and start to fill tubes (20), going down tube (16) and then filling tube (26), and when this happens the air remaining inside tubes (16, 20 and 24) will exit through the said partial closure (2-2′), thus avoiding air pockets which would prevent the thermosyphon from functioning, and if we fill the primary circuit through the other tube (8), the water will fill tubes (21, 16 and 26) and when it reaches tube (25), the air in tubes (20 and 24) will only be able to exit through the space reserved for the passage of air by means of the said closure (2-2′), whereby it may be concluded that if the closure (2-2′) were total, the thermosyphon would not function.
 5. Solar system for heating domestic water according to claim 4, characterized in that the partial closure (2-2′) permits the passage of air and the passage of an insignificant amount of fluid of the primary circuit, meaning that nearly all of the said fluid goes down tube (16), having for this purpose a small air passage.
 6. Solar system for heating domestic water according to claim 1, characterized in that the passage (22) of the fluid in the primary circuit in the exchangers (9 and 10), in conjunction with the passage (19) of the piped water to be heated in the tanks (3 and 4), allows the said tanks (3 and 4) to be highly stratified and to function at different temperatures, in view of the fact that the greater the difference in temperature between the primary fluid that arrives at the heat exchanger (9) from the panel (5) and the piped water in tank (3), the greater the transfer of heat acquired in the panels (5 and 6) to the piped water in the said tank (3).
 7. Solar system for heating domestic water according to claim 6, characterized in that the cold piped water that enters tank (4) on the right-hand side through inlet tube (11) does not mix directly with the hot water that exits the top of tank (3) on the left-hand side through inlet tube (13), which allows the water to be progressively heated in the right-hand tank (4), passing through tube (12) to the lower part of the left-hand tank (3) to be heated further in tank (3).
 8. Solar system for heating domestic water according to claim 1, characterized in that tubes (7 and 8) for filling the primary circuit are placed a few centimetres inside the respective exchangers (10 and 9), with the objective of always having some air in the primary circuit in order to allow room for the increase in volume of the fluid which occurs at high temperatures, in view of the fact that the said circuit has to be closed (23) so that the fluid does not evaporate due to the high temperatures that it reaches. 